The earliest snapshot cameras had very simple lenses. They were designed for taking photographs in bright conditions. Anything other than bright sunlight or very light overcast conditions would make acceptable images unobtainable without flash or some other form of artificial lighting.

This was all very well, but what if you wanted less light in the camera? What if it was too bright? Letting too much light in would overexpose the film. One solution would be to put a neutral density filter over the lens each time but this is cumbersome, inconvenient and unwieldy.

Luckily, the precursors to modern cameras were developed with an addition built into the lens